1. Field of the Invention
The invention relates to a fuel cell in which a liquid fuel or a vaporized fuel obtained by vaporizing the liquid fuel is supplied to an anode catalyst layer.
2. Description of the Related Art
In recent years, various types of electronic devices such as personal computers and mobile telephones have been reduced in size as the semiconductor technology advances, and there have been attempts in which a fuel cell is used as the power source of a small-sized device. A fuel cell has such advantages that it can generate electrical power merely by supplying the fuel and oxidizer thereto, and it can continuously generate power merely by replacing the fuel. Therefore, when the downsizing can be achieved, it would create an extremely advantageous system for the operation of mobile electronic devices. Especially, the direct methanol fuel cell (DMFC) uses methanol having a high energy density as its fuel and can generate an electrical current on the electrode catalyst from methanol. Thus, this cell does not require a reformer, and therefore it can be reduced in size. Since the handling of the fuel is easy as compared to that of a hydrogen gas fuel, it is a hopeful power source for small-sized devices.
Known methods for supplying the fuel of DMFC include a gas supplying DMFC for sending a liquid fuel into the fuel cell with a blower or the like after vaporizing the liquid fuel, a liquid supplying DMFC for directly sending a liquid fuel into the fuel cell with a pump or the like, and an internal-vaporization DMFC as shown in Japanese Patent No. 3413111. The internal-vaporization DMFC discloses a fuel penetration layer which retains the liquid fuel and a fuel transmitting layer that diffuses vaporized components of the liquid fuel retained in the fuel penetration layer, and has such a structure that the vaporized components of the liquid fuel is supplied from the fuel transmitting layer to the fuel electrode.
However, power performance of DMFC are not sufficient as compared with those of fuel cells using the hydrogen gas fuel since resistance of the reaction for internal reforming of methanol is high.